What was found
SHORTLY AFTER TAKEOFF A PASSENGER'S CELL PHONE CAUGHT FIRE WITH RESULTED IN A PASSENGER GETTING BURNED AND DAMAGE TO ROW 12 CARPET AND FLOOR PANEL FIRE DID NOT BURN THROUGH FLOOR PANEL. CREW AND PASSENDERS DEPLOYED OXYGEN MASKS DUE TO FUMES. AFT FIRE EXTINGUISHER WAS USED ALONG WITH THE BATTERY CONTAINMENT BAG AND TWO FIRST AIR KITS. AIRCRAFT RETURNED TO THE FIELD AND EMERGENCY WAS DECLARED. AIRCRAFT LANDED OVERWEIGHT. REMOVED FROM SERVICE. NO DAMAGE FOUND DURING PHASE 1 OVERWEIGHT LANDING INSPECTION. REPLACED FIRST AID KITS AND FIRE EXTINGUISHER AND BATTERY CONTAINMENT BAG. REPLACED BURNT CARPET AND FLOOR PANEL.